purescript-xml

Disclaimer: This is a work in progress. XPath is not completely implemented, and the XML parser is slow.

Provides an XML parser, and type classes and combinators for encoding and decoding XML.

Usage

Parse XML

import Data.XML (parseXML)

xml :: Either String XML
xml = parseXML "<program><hello/><world/></program>"

Decode XML to value

Given the following XML...

<user>
  <id>15dbb07f-92eb-42bb-8898-15df3c67898a</id>
  <loginAttempts>4</loginAttempts>
  <names>
    <firstName><language>english</language><text>John</text></firstName>
    <lastName><language>english</language><text>Backus</text></lastName>
  </names>
  <roles>
    <role>moderator</role>
    <role>admin</role>
  </roles>
  <created></created>
</user>

... We can decode the above into another value by implementing the decodeXML :: XML -> Either String a function from the Data.XML.Decode type class. Data is extracted from XML using XPath queries. Currently, only LocationPath expressions, child axes, name tests, and text node tests are supported.

import Control.Applicative (pure)
import Control.Bind (bind)
import Data.List (List)
import Data.Maybe (Maybe)
import Data.XML (class DecodeXML, decodeXML, (?>), (??>), (?>>))

newtype User = User
  { id :: String
  , login_attempts :: Int
  , name :: String
  , photo :: Maybe String
  , roles :: List String
  }

instance decodeXmlUser :: DecodeXML User where
  decodeXML xml = do
    -- `?>` extracts the first decoded child node from xpath query results
    id <- xml ?> "id/text()"

    -- XML nodes selected by the xpath query are decoded to primitive types, in this case integer.
    -- DecodeXML instances are provided for strings, numbers, and integers.
    login_attempts <- xml ?> "login_attempts/text()"

    name <- xml ?> "names/firstName/text()"

    -- `??>` extracts the first child node from xpath query result as a maybe value
    photo <- xml ??> "photo"

    -- `?>>` returns the list of xpath query result nodes
    roles <- xml ?>> "roles/role/text()"

    pure (User { id, name, photo, roles })

Documentation

Documentation is published on Pursuit.